Method of destructively distilling oil shale in a producer-type of retort



METHOD F DESTRUCTHVELY DISTliLLING OIL SHALE IN A PRDUCER-TYPE 0F RETORTJames W. Martin, Tnckahoe, N. Y., assigner to Carhonic Products, luc.,New York, N. Y., a corporation of New York Application February 26,1953, Serial No. 339,079

12 Claims. (Cl. 202-6) The present invention relates to an improvedmethod of recovering oil, gases, and other by-products from oil shaleand similar kerogen-containing materials, and, more particularly, to animproved method of destructively distilling such materials by using acombustion-supporting gas containing carbon dioxide and oxygen in acritical ratio.

It is well known that heretofore the conventional method of obtainingoil from oil shale involved the initial mining of the shale from theground, the intermediate preparation thereof for thermal treatment inretorts, the subsequent destructive distillation of the thus-preparedshale in retorts `by heat and the recovery of oils and byproducts fromthe vapors and gases distilled from such retorts, and the final removalof the residual spent shale from the distillation Zone of such `retortsand its subse-V quent combustion under the retorts to supply some of theheat. Although attempts were made to overcome difficulties anddisadvantages of prior processes, none, as far as I am aware, wasentirely successful when carried into practice commercially on anindustrial scale.

I have discovered an improved method of destructively distilling oilshale which overcomes the difficulties and disadvantages of priorprocesses and attempts and which provides the art with new results. V

It has likewise been found that in the presence of an excess of carbondioxide (above 40%) in the gases entering the distillation zone thefollowing desirable effects take place:

(a) The carbon dioxide forms loose temporary compounds with thehydrocarbons and tends to make these compounds more volatile and thusmore quickly and completely removed from the shale, and

(b) The carbon dioxide under the foregoing conditions tends to preservecarbon to hydrogen linkagesin the newly formed hydrocarbons therebypreventing the further cracking of these unsaturated and aromatichydrocarbons and simultaneously decreasing the formation of saturatedhydrocarbons of the aliphatic and naphthenic types.

It is an object of the present invention to provide an improved processfor the destructive distillation of oil shale in which gaseous productsof combustion with high heat content and with high carbon dioxidecontent are effectively utilized. Y

It is a further object of the invention to provide an improved processfor the destructive distillation of oil shale wherein means will be usedto limit the formation of hydrogen and light gases of the methane serieswhile at the same time increasing the production of the members of theolefenic and aromatic series.

It is likewise within the contemplation of the invention to provide animproved process for the destructive distillation of oil shale whichwill effect a fixation and recovery of ammonia and similar basicnitrogen compounds.

Among the further objects of the present invention is the provision ofan improved process for the destructive distillation of oil shale whichwill provide combustion- ICC supporting gas containing carbon dioxideand oxygen in a critical ratio, which will prevent relatively hightemperatures in the zone of destructive distillation of oil shale, whichwill maintain relatively low temperatures in the combustion zone, andwhich will bathe the zone of destructive distillation with hot carbondioxide and thus mix carbon dioxide with resultant gaseous hydrocarbons.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the4 accompanying drawing whichillustrates diagrammatically and partly in section the operating portionof a producer-type of retort used on Colorado oil shale.

In my new improved process, oil shale or similar kerogen-containing rawmaterials, such as torbanites, lignites, cannel, and certain othercoals, and carbonaceous ma terials are heated in a retort in anatmosphere supplied with combustion-supporting gas containing carbondioxide and oxygen in a critical ratio whereby the evolved gas and vapordistillates produced are substantially free from aliphatic andnaphthenic hydrocarbons and are rich in the commercially many times morevaluable unsaturated and aromatic hydrocarbons and the compounds similarto aromatic hydrocarbons, but having sulfur, oxygen or nitrogen in theircomposition, such as derivatives of pyridine, quinoline, thiophen,cresols, etc. For the purpose of the present specification, the latterring-type products will be considered as included within the expressionaromatic compounds.

Broadly stated, the present invention contemplates a Vsolution to thevexatious problem confronting the art in effecting combustion of fixedcarbon of oil shale by a gaseous mixture of oxygen and carbon dioxide incritical proportions or ratios. By utilizing special mixtures containingoxygen or air and carbon dioxide in critical proportions or ratios, arelatively low and regulated temperature can be obtained. Thetemperature in the combustion zone within the oil shale structure ispreferably kept well below about l000 C. to limit the formation ofcarbon monoxide. Furthermore, the temperatures in the zones ofdestructive distillation are controlled to a temperature range aboveabout 400 C. and below about 600 C., and preferably within a range ofabout 425 C. to about 550 C. Such critical regulation can be effected bycontrolling the ratio of carbon dioxide to oxygen (or air) in theoxidizing gas fed into the combustion zone as will be explained indetail hereinafter.

Generally speaking, my improved process for the destructive distillationof oil shale contemplates the following features and operations:

1. The maintenance of predetermined, controlled and criticaltemperatures, such as from about 400 C. to about 600 C., in thedistillation zone of a system for the distillation of hydrocarbons fromkerogen-containing natural substances. v

2. The use of a uid chemical, such as carbon dioxide, having theproperty of preserving the carbon-hydrogen linkages of the hydrocarbonsformed or evolved during the process of distillation.

3. The use of a gas which will promote the formation of unsaturatedhydrocarbon gaseous and liquid cornpounds.

4. The use of a gas which will promote the formation of aromatic gaseousand liquid compounds.

5. The use of a fluid which is of acid nature so as to tix and rendernon-volatile at condenser temperatures, the ammoniacal compoundsdistilled.

6. The use of a gaseous catalyst, carbon dioxide.

In carrying the invention into practice, it is preferred to control thecombustion temperature by the use of a predetermined and criticaloxygenzcarbon dioxide ratio in the oxidizing gas. The critical ratioscan be varied from about 30% to about 80% carbon dioxide. InV

order to control combustion in an oxidizing air mixture, carbon dioxidein the optimum proportion possible (say about 40%) is preferred, or upto 80% of carbon dioxide when oxygen gas is used. Such mixtures willconvey the needed heat from a combustion zone to a zone in which theheat is required (reaction or distillation zone).

Carbon dioxide can be separated from the resulting iixed gases bypartial liquefaction by compression, by dissolving the former in waterunder pressure in a carbon dioxide separator or by means of chemicals;and the remaining gases, mostly combustible, may be either furtherseparated or used as such for fuel.- In some cases, where thecombustible gases mixed with the carbon dioxide are in -relatively largeamounts, this separation process may be omitted and the whole gasmixture used as fuel,

The atmosphere in which thedistillation of the kerogencontainingmaterial is heated is found to be inetective in the present process whenthe percentage of carbon dioxide reaching the distillation zone is below30% but is increasingly elec'tive as the percentage of carbon dioxiderises to and above 40% and until at 80 to 100% carbon dioxide, withexternal heating of the retort, there are essentially only unsaturatedand aromatic (including heterocyclic ring compounds) oil and gaseouscompounds formed. Dilution of the heating atmosphere with steam inmoderate percentages does not seem to affect adversely the process andaids in the control of the temperatures of the combustion anddistillation zones.

It will be noted that the carbon dioxide is not destroyed in the processand that carbon dioxide ine-the percentages used acts as a catalyst.This is one of the few cases r perhaps the only known case where carbondioxide acts as a catalyst to changeY the course'of a chemicalreaction.'

about 375 C. is required, somewhat higher temperatures such as 450 C.serve to speed up this production of oil, ctc., but use of much highertemperatures, of say 550 C. to 600 C. are objectionable in that-oilcracking occurs with destruction of the earlier formed more valuableproducts. In my present process where a high carbon dioxide atmosphereis present, these reaction temperatures are not substantially changed.

In my improved process, the exit hydrocarbon gases will consistessentially of ethylene, propylene and butylenes, together with theheating gases (now cooled) of hydrogen, carbon dioxide and nitrogen,small amounts of carbon monoxide, ammonia, water vapor, and but tracesof hydrogen sulfide, oxygen and methane.

The liquid condensate consists essentially of unsaturated hydrocarbons,aromatic hydrocarbons and the heterocyclic products closely related tothe aromatic hydrocarbons and often spoken of as aromatic because manyof their chemical properties are closely similar to those of thearomatic hydrocarbons. Of course, there will be traces of the gasesmentioned hereinbefore dissolved in this oily mixture as first condensedbut the amounts are insignificant. Saturated compounds, such asaliphatic hydrocarbons and naphthenes are absent and thereby distinguishthis oily product from well petroleum or normal shale oil or similarproducts.

In the last two decades, there has developed a huge petrochemicalindustry, essentially an aliphatic chemical industry based on additionproductsmade `from -unsatu` rated hydrocarbons, e. g., automobileanti-freeze glycols made from mixtures of ethylene and propylenehydrocarbons, Petroleum gases and liquids normally carry no unsaturatedhydrocarbons such as ethylene and propylene and to obtain thesepetroleum has to undergo a severe and expensive cracking andpurification process. By my invention, the cheap raw gases obtained inthe retorting can at Y once, even though mixed with other gases, be usedas starting materials for such aliphatic petrochemicals production. Forother products used as raw materials for petrochemicals the liquidunsaturated hydrocarbons are also Well adapted.

In World War II, there began the production of aromatics such as benzoland toluol by a succession of expensive chemical and physical steps fromsaturated petroleum hydrocarbons, particularly the six and seven carbonatom aliphatic hydrocarbons, and this production has and will increasefor many years as these products form the basis of our more importantthermo-setting and thermo-plastic resins, plastics, synthetic rubber,explosives and some of the newer textiles, etc. In the production ofthese products, one of the catalysts used is platinum and the process isspoken of as the platforming process.

The liquid product formed by my improved process is largely aromaticand, as such, it will be cheaper and a much more advantageous materialfor the production of aromatic chemicals than the crude well petroleumnow used.

Heat is the primary agent for obtainingvolatile hydrocarbons, etc., fromnatural material containing kerogen. Such pyrolysis leaves in the ash anon-distillable carbon residue ordinarily called coke, e. g. oil shalecoke or more simply shalecoke Such coke can be burned and the resultingheat used to destructively distill the kerogen to produce the oils andvapors wished.

Formerly the oil shale or other kerogen-containing material was placedin stationary or rotating retorts and heat applied externally throughthe wall of the retort. Later years have developed processes where theheat is applied internally, mostly by the use of retorts built on theprinciple of a gas producer.

For my new process many types of equipment can be used but I prefer aretort based on the design of the modern water-jacketed stationary gasproducer with a moving ash grate, such as the common Wellman- Galushagas producer. However, in operation of such an internally heated retortmuch lessfair is fed than when producer gas is the desired product, inorder that the pyrolysis can be carried out at the much lowertemperature required to avoid burning or over-cracking the oil produced.

The volumes of air andV of carbon dioxide and of steam, if steam isused, will vary with the percentage of kerogenl present in the materialbeing fed the retort, the sizeof the lumps offeed material, thecharacter of the oil and gas products desired and for other reasons, andalso with the low operating temperatures desired in the kerogenpyrolysis zone (distilling or reaction zone). Low temperatures favorunsaturates, higher temperatures, the aromatics.

g The accompanying drawing illustrates a vertical section through theoperating portion of al producer type retort used on a Colorado oilshale capable of yielding 25 gallons oil per ton of oil shale for theproduction primarily of unsaturated and aromatic hydrocarbons as rawmaterials for petrochemical operations. Entering the distillation zone,the heating gases have 40% or higher carbon dioxide content, but theoxidizing gas mixture fed at the bottom of the retort to produce thisratio needs to contain only 30% carbon dioxide. The-ratio of carbondioxide to oxygen in the feed gasto shale coke zone as given isapproximately two volumes to one, i. e., 30% carbon dioxide to 14%oxygen, or 30% carbon dioxide, 70% air (3% air is oxygen). Two to oneisa low ratio. For high ratios commercial oxygen would be added to thefel' aisil'pply.

For the purpose of giving those skilled in the art al betterunderstanding of the invention, the following illustrative examples aregiven:

Example I Example Il When 40% carbon dioxide is used in the distillationzone, the composition of the crude shale oil and gas was 5% saturates,60% unsaturates and 16% true aromatics.

Example III Using an externally heated retort operating at 400 to 500 C.and continually running in a slow stream of 100% carbon dioxide at aboutatmospheric pressure so that the oil shale was continually in contactwith only carbon dioxide and its own vapors as the pyrolysis proceeded,the oil and gas resulting contained no saturates (parafiins andnaphthenes), but did contain 68% unsaturates, and 20% true aromatics.

Example IV For comparison with Example III another run was made using aninert gas atmosphere instead of the chemically active carbon dioxide gasbut otherwise the same conditions. The inert gas used was nitrogencontinually run in as a slow stream of 100% nitrogen at the same rate,same pressure, same operating temperature and using the same equipmentand other conditions except that the oil shale was continually in-contact only with nitrogen and its own vapors as the pyrolysisproceeded, the oil and gas resulting contained 15% of saturates and 50%unsaturates and 33% of aromatics.

Those skilled in the art will appreciate the surprising result broughtabout by the presence of carbon dioxide in accordance with the presentinvention. The foregoing were all run at about 500 C. in thedistillation zone. Other research work and tests show that whenoperation is at a somewhat higher temperature, the percentage ofaromatics can be doubled but at a sacrifice of the percentage ofunsaturated hydrocarbons.

It is to be noted that the present invention is not to be confused withthe process of oil shale distillation commercially used in Estoniawherein a mixture of air and steam, but no carbon dioxide, is used toburn the shale coke at a temperature above 1000 C. in brick-linedrotating producer-type retorts. Nor should the present invention beconfused with the gas-combustion process developed in 1951 by the U. S.Bureau of Mines using the small (1 8" diameter) experimental retort atRie, Colorado. In this shale retort, a combustion temperature of 770 C.is produced by burning a mixture of air and wet recycled gas previouslyproduced in this process. This recycled gas has a heating value of but85 B. t. u. per cubic foot and a typical analysis of the dry gas exitshows 24% carbon dioxide, 60% nitrogen, 12% combustibles, besides themoisture. It requires a fourth its volume of air to burn itscombustibles. Accordingly, the feed mixture to the combustion zone willcarry only about 17% carbon dioxide and the distillate obtained by thepyrolysis of the kerogen will be largely saturated hydrocarbon withlesser quantities of olefenic and aromatic hydrocarbons-just the reverseof that given by the present invention.

It will be noted that while both of these processes use equipmentsomewhat similar to that used in the process of present invention, theprocesses themselves are quite different. Both use much` highertemperatures (1000 C. and 770 C.) and much lower percentages (0% and17%) of carbon dioxide than does the present process of at least 30% inthe feed gas and 40% at the top of the combustion zone. Moreover, theresult of the process shows up in the change in the character of the oiland gas produced, being essentially of the olefenic and aromatic insteadof primarily aliphatic hydrocarbons.

The present application is a continuation-in-part of my co-pendingpatent application, Serial No. 64,401.

Although the present invention has been described in conjunction withpreferred embodiments, itis to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

l claim:

l. An improved method of destructively distilling oil shale and similarkerogen-containing natural materials in a retort to produce oil andgases which comprises heating saidmaterial to a temperature of about 300to 500 degrees C. in an atmosphere containing oxygen and more than 40%carbon dioxide, said carbon dioxide and oxygen in said atmosphere beingin the ratio of at least two to one.

2. An improved method of destructively distilling oil shale and similarkerogen-containing natural materials in a producer-type of retort toproduce oils, gases and ash which comprises establishing a column havinga cold zone on the top and a hot ash zone on the bottom with apreheating zone, a distillation zone, a hot zone, and a re zone inbetween; feeding kerogenous material to the top of said column,withdrawing hot ash from the bottom of said column, blowing acombustion-supporting gas containing carbon dioxide and oxygen in aratio of at least 2 to 1 upwardly and through the aforesaid zones toburn hot shale coke in said lire zone and to produce hot gas at atemperature of about 350 to 450 degrees C., passing said hot gascontaining upwards of 40% carbon dioxide into the shale Zone to causedistillation of oil vapors and gas to continue to flow upwardly topreheat the kerogenous material in said preheating zone coming from saidcold zone; removing oil mist, vapors and gas coming off said cold zone;conveying said oil mist, vapors and gas to a separator to condense oiland by-products while permitting gas to go to a holder.

3. The improved method set forth in claim 2 in which the temperature ofthe vapors and gas flowing upwardly from about C. through the hot ashzone, to above 500 C. in the lire zone, and passing through the hotshale coke zone decreasing to about 450 C. in the distillation zone andto about 400 C. in the preheating zone and to about 350 C. in thegaseous zone while the temperature of the shale moving downwardly in thecolumn iA creases from about 30 C. in the gaseous zone to about C. inthe cold zone, to about 250-350 C. in the preheating zone, to about400-450 C. in the distillation zone, to about 500 C. in the hot shalecoke zone and to about 600 C. in the lire Zone and then to decrease thetemperature to about 300 C. in the hot ash zone.

4. The improved method set forth in claim 2 in which thecombustion-supporting gas contains about 30% carbon dioxide and 70% air.

5. The improved method set forth in claim 1 in which the carbon dioxideis varied from about 40% to about 80% and the resulting oil and gascontains less than 15% of saturates, from 35% to 68% unsaturates andfrom 5% to 20% aromatics.

6. In the method of destructively distilling oil shale and similarkerogen-containing natural materials in a producer-type of retort toproduce oil, gases, and other products that improvement which comprisesheating said materials to a temperature of about 350 C. to about 450 C.in an atmosphere of about 30% to about 80% ofk carbon dioxide andcontaining carboni dioxideA andv oxygen in a ratio Vof-at least2 to 1-.

7. In they method ofi destructively distilling2 oil shale andsimilarirkerogen-containingv natural materials in a retort to produce oil, gasesandother products that im* provernent Whichcomprises using` at least 30%of carbonV dioxide at atemperature of about350to'450 degrees C. asargaseouszcatalystinthef presence of oxygen for increasingthev'productiorr of unsaturated 'and aromatic hydrocarbons in thethermal decomposition of said materials, said carbon dioxide and oxygenbeing present in a ratio of vatleastZto l.

8. In, the method of destructively` distilling oil shale and similarvkerogen-containing n-atural'materialsfin a retort to produce oil, gasesand'other products that irnprovement-which'comprisesutilizing gaseousproducts of combustionat'a temperature of about 350 to 450 degrees C.with high heat content and with high carbon dioxide content of at least30% in the presence of oxygen to eiectively distill said=kerogen`ous`materials, said carbon dioxide and oxygen being present in a ratio of atleast 2 to -1.

9. In the method of destructively distilling oil shale and similarkerogen-containing natural materials in a retort toproduce oil, gasesand other products that irnprovementwhich comprises' usingacombustion-supporting Ygas containingcarbondioxide and oxygen inacritical ratio of atleast 2 to l tolmaintain a temperature in the zoneof destructive distillationvin the range` of 350 to 450 degrees C. whilebathing the zone of destructive distillation with hot carbon-dioxidepresent to an extent of at least 30% 'and mixing carbon dioxide -wtihevolved hydrocarbons. v

l0.V Themethod set forth lin' claim 9 in which the temperature lincombustion Zone is keptA below 600 C. to limit the formation ofcarbon-monoxide and the ternperatrsre 'in the distillationfzone iscontrolled within a range of about 350 to 450 degrees C.

l1. The method set forth in claim 9 in which the critical ratio can bevaried by varying the carbon dioxide from about 30% to about-80%.

12, The method set'forth in claim 9 -in which carbon dioxide isseparated from the-evolved hydrocarbons andV gas and reused in thecombustion-supporting gas.

References Ctedin the le of this patent UNITED STATES PATENTS` 1,509,667.Carlin se'pfgzs, 1924 f FOREIGN PATENTS 346/26 Australia D66. 14, 1926

1.AN IMPROVED METHOD OF DESTRUCTIVELY DISTILLING OIL SHALE AND SIMILAR KEROGAN-CONTAINING NATURAL MATERIALS IN A RETORT TO PRODUCE OIL AND GASES WHICH COMPRISES HEATING SAID MATERIAL TO A TEMPERATURE OF ABOUT 300 TO 500 DEGREES C, IN AN ATMOSPHERE CONTAINING OXYGEN AND MORE THAN 40% CARBON DIOXIDE, SAID CARBON DIOXIDE AND OXYGEN IN SAID ATMOSPHERE BEING IN THE RATIO OF AT LEAST TWO TO ONE. 